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Testing Visual Acuity (VA) Initial part of any ophthalmic examination/photography/treatment Initial part of any ophthalmic examination/photography/treatment A National grading protocol A National grading protocol Visual performance is dependent on Visual performance is dependent on –Integrity of retina, visual pathway –Quality of retinal image –Ambient light level

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Snellen Test Type Standard method – in Tayside the software converts Snellen to LogMAR Standard method – in Tayside the software converts Snellen to LogMAR Not very sensitive for poorer visual acuities Not very sensitive for poorer visual acuities The progress of letter sizes is unequal The progress of letter sizes is unequal Get a crowding effect Get a crowding effect Not mathematically sound Not mathematically sound

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EDTRS chart LogMAR Recommended Gold Standard Recommended Gold Standard Better chart design Better chart design High contrast lettering High contrast lettering Letters set at equal linear steps, equal spacing Letters set at equal linear steps, equal spacing Contains a near equal score of difficulty on each line Contains a near equal score of difficulty on each line More effective analysis and comparison of results More effective analysis and comparison of results

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LogMAR Patient seated at 2m Patient seated at 2m Separate chart for each eye Separate chart for each eye More consistent level of illumination More consistent level of illumination

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Recording VA If only half of line read If only half of line read e.g. 3/9 Record as either 3/9 minus no. of letters missed or 3/12 + number of letters seen on 3/9 line

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If unable to see any letters and if practical move chart nearer to patient If unable to see any letters and if practical move chart nearer to patient Or examiner holds up hand at 1m, patient asked to count fingers (CF) Or examiner holds up hand at 1m, patient asked to count fingers (CF) If unable to CF then examiners hand is moved in front of patients eye (HM) If unable to CF then examiners hand is moved in front of patients eye (HM) Failure to see examiners hand move Failure to see examiners hand move Check with pen torch perception of light (POL) Check with pen torch perception of light (POL) If no light seen by patient (NPL) If no light seen by patient (NPL)

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Using Pin-hole If reading less than 3/6 then use pin-hole If reading less than 3/6 then use pin-hole Allows only central light rays into eye along the visual axis Allows only central light rays into eye along the visual axis Eliminates blurring of vision if refractive error present Eliminates blurring of vision if refractive error present Using patient’s hand - risk of error, may not fully occlude their eye Using patient’s hand - risk of error, may not fully occlude their eye

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Pin-hole If acuity improves it usually indicates refractive error e.g. cataract If acuity improves it usually indicates refractive error e.g. cataract If VA worse through pin-hole over best correction macular disease must be considered If VA worse through pin-hole over best correction macular disease must be considered

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Adverse event following mydriasis Patient knows how to access advice Patient knows how to access advice Tayside have a 24 hour point of contact at Ophthalmology ward 25, Ninewells Tayside have a 24 hour point of contact at Ophthalmology ward 25, Ninewells Availability of on call Ophthalmologist if patient symptoms necessitate review Availability of on call Ophthalmologist if patient symptoms necessitate review

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